Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
  • C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
  • C07C29/94—Use of additives, e.g. for stabilisation
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
  • C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
  • C07C29/88—Separation; Purification; Use of additives, e.g. for stabilisation by treatment giving rise to a chemical modification of at least one compound

Definitions

• the present invention relates to a method for deodorising 1,2-alkanediols.
• the process is characterized in that malodorous organic impurities are purified in mixtures comprising 1,2-alkanediols, such as are usually obtained after the synthesis from the corresponding 1-alkenes.
• the 1,2-alkanediols are deodorized by separating them from the organic impurities by distillation, the mixture to be purified being mixed with an additive before or during the separation by distillation.
• the additive is at least one oxide or halide of iron or aluminum.
• the 1,2-alkanediols deodorized by the process according to the invention are particularly suitable for use in cosmetic products or in household cleaning products.
• 1,2-Alkanediols are widely used in cosmetics, household products and technology. They have moisturizing properties, can be used as solubilizers and are chemically stable. These and other properties make them ideal for the applications mentioned.
• EP 0 655 904 B1 describes the use of 1,2-alkanediols, in particular 1,2-pentanediol, in skin-moisturizing agents.
• EP 1 478 231 B1 describes mixtures of at least two 1,2-alkanediols, for example 1,2-hexanediol and 1,2-octanediol, with improved antimicrobial properties.
• EP 1 598 064 B1 describes the use of mixtures of an alkanediol and a hydroxylated acid against acne.
• EP 2 842 607 A1 describes the use of mixtures of alkanediols, resorcinol derivatives and bisabolol in skin-lightening products.
• WO 2006/069953 A1 describes mixtures of at least two components selected from 1,2-pentanediol, 1,2-hexanediol and 1,2-octanediol. Such mixtures can be used as formulations for moisturizing the skin.
• WO 2019/029808 A1 describes a process for the production of particularly pure 1,2-alkanediols which, due to their high purity, are well suited for use in cosmetic formulations and household products.
• DE 32 29 084 A1 describes a process for the preparation of vicinal diols in which 1-alkenes are reacted with hydrogen peroxide and formic acid and the formate esters thus obtained are then converted into the corresponding 1,2-alkanediols by decarbonylation.
• the 1,2-alkanediols are purified by distillation.
• KR-10-2015-0122854 A describes a process for the production of 1,2-hexanediols with high purity.
• 1-hexene is reacted with formic acid and H 2 O 2 in the presence of iron (III) salts such as FeCl 3.
• EP 1 671 936 A2 describes a process for the production of vicinal alkanediols and alkanetriols, in which monoolefins are reacted with H 2 O 2 and formic acid.
• the formates obtained are transesterified with methanol in the presence of an arylsulfonic acid and the 1,2-alkanediol is distilled from the corresponding mixture.
• a problem with the synthesis of 1,2-alkanediols via the routes described is the formation of organic by-products. This is problematic because these 1,2-alkanediols are typically incorporated into consumer products. For this reason alone, when processing 1,2-alkanediols in consumer goods, it is necessary to use them as pure as possible. The problem becomes even more explosive because one of the main areas of application for 1,2-alkanediols is cosmetic products. The separation of organic impurities, especially if they are bad-smelling, is particularly important here.
• DE 199 29 196 A1 describes a process for the preparation of vicinal diols from the corresponding alkenes with H 2 O 2 and formic and / or acetic acid to give the corresponding esters.
• the reaction is carried out without the addition of an organic solvent, as a result of which a two-phase product mixture is formed.
• An organic solvent is added to this and excess water and formic and acetic acid are distilled off azeotropically.
• the residue is saponified and water is distilled off azeotropically from the residue using an organic solvent.
• the organic phase comprises the intermediately formed mono- and diesters of the diol with formic acid or acetic acid.
• the aqueous phase comprises excess H 2 O 2 and unreacted acetic acid or formic acid.
• phase transfer catalysts which accelerate the reaction, are added to the reaction mixture.
• Lewandowski Polish Journal of Chemical Technology 2013, 15, 96-99 also describes quaternary ammonium salts in the preparation of vicinal diols from 1,5,9-cyclododecatriene with H 2 O 2 and dodecatungstophosphoric acid.
• phase transfer catalysts in the synthesis of vicinal diols represents an improvement of the process, since it leads to an increased reaction rate.
• it leads to a further problem, which must be taken into account when the vicinal alkanediols obtained are used in cosmetics and household products.
• a bad odor was observed which cannot be completely removed even after renewed distillation. This odor also appears in part in the 1,2-alkanediol obtained.
• the inventors of the present invention suspected that this odor was due to the use of the quaternary ammonium salts, which decompose during the distillation of the product. It was also suspected that amine decomposition products are dragged along with the purification by distillation and that immediately or after a while lead to the bad odor in the 1,2-alkanediol.
• the object of the present invention was accordingly to provide an improved process for the preparation of 1,2-alkanediols which does not have the disadvantage mentioned and in particular, while maintaining the advantages that a phase transfer catalysis of the reaction brings with it, to 1 , 2-alkanediols with improved odor quality.
• the characterizing step of the process according to the invention comprises the provision of the alkanediol of the formula (I) in a mixture M comprising, in addition to the alkanediol of the formula (I), organic impurities V.
• This mixture M can arise in various ways. In particular, however, it is obtained by one of the processes described in the prior art in which the alkanediol of the formula (I) is reacted, starting from the 1-alkene of the formula (II) mentioned below, by reaction with H 2 O 2 and formic acid or acetic acid obtained formates or acetates are saponified and the crude product is distilled. The distillate is then the mixture M.
• the process according to the invention is particularly efficient and therefore preferred if quaternary alkylammonium compounds are used during this synthesis, which are then found in particular in the crude product. These decompose at least partially during the distillation and form amine organic impurities, which can be removed particularly well with the process according to the invention.
• the method according to the invention is also suitable, however, the WO 2019/029808 A1 to remove the malodorous lactones described.
• the process according to the invention can also be used for the deodorization of 1,2-alkanediols which are present in mixtures obtained by other processes, for example by epoxidation of an alkene by means of tungsten catalysis and subsequent ring opening to 1,2-alkanediol.
• a further synthesis is also possible by reacting the alkene with sodium hypochlorite and acidic opening of the epoxide formed.
• the organic impurities V can be recognized by their odor, which is perceived as bad by the human nose, and are therefore foul-smelling.
• the organic impurities V are accordingly in particular those from the group of the ketones, lactones and amines, especially amines.
• Lactonic organic impurities V are typically organic ring-shaped compounds which have an ester group in the ring and which result as by-products in particular in the reaction of the 1-alkene used with H 2 O 2 and the respective acid to form the mono- or diester or in the decomposition this ester under the reaction conditions of the process according to the invention.
• Lactonic impurities are preferably lactones with 4 to 14 carbon atoms, in particular with 4 to 12 carbon atoms.
• Organic impurities V which are ketones, arise as by-products in particular during the reaction of the 1-alkene used with H 2 O 2 and the respective acid to form the mono- or diester or during the decomposition of these esters under the reaction conditions of the process according to the invention.
• Such ketones preferably have 4 to 14 carbon atoms, in particular 4 to 12 carbon atoms.
• Ketones have a carbonyl carbon bonded to two carbon atoms.
• Particularly suitable aminic organic impurities V are those which result from the decomposition of the quaternary ammonium salts according to the invention. These can be, for example, aliphatic amines or aromatic amines, preferably aliphatic amines, aliphatic amines preferably comprising secondary or tertiary alkylamines.
• the at least one alkanediol of the formula (I) is at least partially separated off from the organic impurities V present in the mixture M.
• a composition is obtained in which the mass fraction of the organic impurities V , based on the mass of all alkanediols of the formula (I), is less than the mass fraction of the organic impurities V , based on the mass of all Alkanediols of the formula (I), in the mixture M.
• the provided alkanediol of the formula (I) in a mixture M comprising at least one alkanediol of the formula (I) and organic impurities V is in the process according to the invention according to one of the following steps ( ⁇ ), ( ⁇ ) or ( ⁇ ) at least partially from the organic Impurities V separated. It is preferably at least partially separated from the organic impurities V after one of the following steps (a) or ( ⁇ ), more preferably after step ( ⁇ ).
• the mixture M is mixed with at least one additive Z in a first sub- step ( ⁇ 1), whereby a mixture M a1 comprising at least one alkanediol of the formula (I), at least one additive Z and the organic impurities V is obtained.
• the additive Z is added in sub- step ( ⁇ 1 ) in particular in such an amount that the mass fraction of all additives Z based on the mass of all alkanediols (I) comprised by the mixture M is in the range 0.01 to 10% by weight, preferably 0.1 to 5% by weight, more preferably 0.2 to 3% by weight, most preferably 0.5 to 2% by weight, most preferably 1 to 1.5% by weight.
• a mixture M a1 comprising at least one alkanediol of the formula (I), at least one additive Z and the organic impurities V is then obtained.
• the at least one alkanediol of the formula (I) is then at least partially separated off by distillation from the mixture M a1 in sub- step ( ⁇ 2).
• the alkanediol of the formula (I) can be separated off by distillation by processes known to the person skilled in the art, such as, for example, in US Pat WO 2019/029808 A1 , Paragraph [0270].
• composition comprising the purified at least one alkanediol of the formula (I) is then obtained.
• the mixture M is mixed with at least one additive Z in a first sub-step ( ⁇ 1 ), whereby a mixture M a1 comprising at least one alkanediol of the formula (I), at least one additive Z and the organic impurities V is obtained.
• the additive Z is added in sub-step ( ⁇ 1 ) in particular in such an amount that the mass fraction of all additives Z based on the mass of all alkanediols (I) comprised by the mixture M is in the range 0.01 to 10% by weight, preferably 0.1 to 5% by weight, more preferably 0.2 to 3% by weight, most preferably 0.5 to 2% by weight, most preferably 1 to 1.5% by weight.
• a mixture M a1 comprising at least one alkanediol of the formula (I), at least one additive Z and the organic impurities V is then obtained.
• a substep ( ⁇ 2) the additive Z is then removed again from the mixture M a1. This is done in particular by decanting or filtration, in particular by filtration.
• the mixture M a1 is stirred between substeps ( ⁇ 1) and ( ⁇ 2), preferably for at least 10 seconds to 1 hour, more preferably 1 minute to 30 minutes, even more preferably 5 minutes to 10 minutes . This ensures that the Mixture M a1 comprised impurities V react with the additive Z and / or are adsorbed.
• a mixture M a2 comprising at least one alkanediol of the formula (I), at least one additive Z and the organic impurities V is obtained, the content of additive Z in the mixture M a2 being reduced compared to M a1.
• the content of the organic impurities V in the mixture M a2 based on the content of all alkanediols of the formula (I) in the mixture M a2 , compared to the content of the organic impurities V in the mixture M a1 , based on the content of all , is also preferred Reduced alkanediols of the formula (I) in the mixture M a1 . This is particularly the case when impurities V react with the additive Z and / or are adsorbed. If they are adsorbed, they are then separated off with the addition of Z.
• a mixture M a2 comprising at least one alkanediol of the formula (I), at least one additive Z and the organic impurities V is obtained in a preferred embodiment, the content of additive Z in the mixture M a2 being based on the content of all alkanediols of the formula (I) in the mixture M a2 , compared to the content of the additive Z in the mixture M a1 , based on the content of all alkanediols of the formula (I) in the mixture M a1 , by at least 50%, is preferably reduced by at least 75%, more preferably by at least 90%.
• the content of all organic impurities V in the mixture M a2 based on the content of all alkanediols of the formula (I) in the mixture M a2 , compared to the content of all organic impurities V in the mixture M a1 , based on the Content of all alkanediols of the formula (I) in the mixture M a1 reduced by at least 50%, preferably by at least 75%, more preferably by at least 90%.
• step ( ⁇ 2) the additive Z is only partially separated off from the mixture M a1.
• a mixture M a2 comprising at least one alkanediol of the formula (I)
• at least one additive Z and the organic impurities V is obtained, the content of additive Z in the mixture M a2 , based on the content of all alkanediols of the formula (I) in the mixture M a2 , compared to the content of the additive Z in the mixture M a1 , based on the content of all alkanediols of the formula (I) in the mixture M a1 , by 50% to 99.99%, preferably by 75% to 99.0%, more preferably by 90% to 98%.
• the content of all organic impurities V in the mixture M a2 based on the content of all alkanediols of the formula (I) in the mixture M a2 , compared to the content of all organic impurities V in the mixture M a1 , based on the Salary of everyone Alkanediols of the formula (I) in the mixture M a1 are reduced by 50% to 99.99%, preferably by 75% to 99.0%, more preferably by 90% to 98%.
• the at least one alkanediol of the formula (I) is then at least partially separated off by distillation from the mixture M 32 in sub-step ( ⁇ 3).
• the alkanediol of the formula (I) can be separated off by distillation by processes known to the person skilled in the art, such as, for example, in US Pat WO 2019/029808 A1 , Paragraph [0270].
• composition comprising the purified at least one alkanediol of the formula (I) is then obtained.
• the alkanediol of the formula (I) is at least partially separated off from the mixture M by distillation.
• At least one additive Z is added to the mixture M during the separation of the alkanediol of the formula (I) from the mixture M by distillation.
• the additive Z is added in step ( ⁇ ) in particular in such an amount that the mass fraction of all additives Z based on the mass of all alkanediols (I) comprised by the mixture M is in the range 0.01 to 10% by weight, preferably 0.1 to 5% by weight, more preferably 0.2 to 3% by weight, most preferably 0.5 to 2% by weight, most preferably 1 to 1.5% by weight.
• step ( ⁇ ) preferably during the distillation, before the proportion of all alkanediols of the formula (I) remaining in the distillation residue falls below less than 50%, more preferably less than 75%, even more preferably less than 90% of the amount, which were used in the mixture M.
• step ( ⁇ ) can be combined with step (a) in such a way that additive Z is added to the mixture M a1 in substep ( ⁇ 2 ) according to step ( ⁇ ).
• step ( ⁇ ) can be combined with step (ß) in such a way that additive Z is added to mixture M 32 in substep ( ⁇ 3) according to step ( ⁇ ).
• the mixture M is preferably prepared as follows:
• step (a) of the preferred process according to the invention an alkene of the formula (II) with H 2 O 2 and at least one acid S selected from formic acid, acetic acid, preferably formic acid, in particular in the presence of a quaternary ammonium salt of the formula K N A, where K N is the cation of the quaternary ammonium salt and A is the anion of the quaternary ammonium salt.
• R is an unbranched or branched, preferably unbranched, alkyl radical having 1 to 10 carbon atoms.
• R is an unbranched or branched, preferably unbranched, alkyl radical having 1 to 8 carbon atoms.
• R is more preferably an unbranched or branched, preferably unbranched, alkyl radical having 1 to 6 carbon atoms.
• R is even more preferably an unbranched or branched, preferably unbranched, alkyl radical having 1 to 4 carbon atoms.
• R is even more preferably an unbranched or branched, preferably unbranched, alkyl radical having 2 to 3 carbon atoms.
• Most preferably R is an unbranched carbon radical with 3 carbon atoms, in which case the structure of the formula (II) is 1-pentene and the structure of the formula (I) is 1,2-n-pentanediol.
• H 2 O 2 is typically used as an aqueous solution, the concentration of the H 2 O 2 in the aqueous solution usually being 30 to 50% by weight, preferably 50% by weight.
• the molar ratio between the amount of H 2 O 2 used in step (a) of the process according to the invention to the amount of all compounds of structure (I) used in step (a) of the process according to the invention is in the range 1: 2 to 3: 1 , preferably 1: 1 to 2: 1, most preferably 1.25: 1 to 1.5: 1.
• step (a) at least one acid S selected from formic acid and acetic acid is also used.
• Formic acid is preferably used since it can be removed particularly easily by decarbonylation in subsequent step (b).
• the molar ratio between the total amount of acid S used in step (a) of the process according to the invention to the amount of all compounds of structure (I) used in step (a) of the process according to the invention is in the range 1: 1 to 20: 1, preferably 1.5: 1 to 15: 1, more preferably 2: 1 to 10: 1, most preferably 2: 1 to 2.5: 1.
• a quaternary ammonium salt of the formula K N A, where K N is the cation of the quaternary ammonium salt and A is the anion of the quaternary ammonium salt is used in step (a) of the process according to the invention.
• quaternary ammonium cation K N as used herein is intended to refer to a cation which contains at least one nitrogen atom which carries a positive electrical charge, the nitrogen atom being bonded only to carbon atoms.
• the nitrogen atom can be saturated, i.e. bound to four carbon atoms through single bonds, or it can be unsaturated, i.e. it can be bound to two carbon atoms through single bonds and to a third carbon atom through a double bond. If the nitrogen atom is unsaturated, it can be part of a heteroaromatic ring such as an imidazolium cation or a pyridinium cation.
• the nitrogen atom When the nitrogen atom is saturated it can be part of an alicyclic ring such as a pyrrolidinium or a piperidinium cation.
• the nitrogen atom is preferably bonded to four substituted or unsubstituted hydrocarbon groups which can carry additional substituents on carbon atoms which are not bonded to the nitrogen atom and which carry a positive electrical charge.
• hydrocarbon group refers to a monovalent radical derived from a hydrocarbon and can include alkyl, cycloalkyl, alkenyl, alkynyl, or aryl groups.
• R Q2 , R Q3 , R Q4 are each independently selected from the group consisting of an alkyl group having 1 to 40, preferably 1 to 35, more preferably 1 to 30, even more preferably 1 to 25 carbon atoms, even more preferably 1 to 18 carbon atoms, even more preferably 4 to 18 and most preferably 4 to 16 carbon atoms are selected.
• Tetrabutylammonium is most preferred as the cation K N.
• anion A used here is intended to refer to the anion of the quaternary ammonium salt, which in particular is selected from the group consisting of phosphate, phosphonate, alkyl phosphonate, monoalkyl phosphate, dialkyl phosphate, bis [trifluoromethanesulfonyl] imide, (halo) alkyl sulfonate, (halo) alkyl sulfate , Bis [fluorosulphonyl] imide, halide, dicyanamide, hexafluorophosphate, sulphate, tetrafluoroborate, trifluoromethanesulphonate, perchlorate, hydrogen sulphate, (halo) alkyl carboxylate, bisoxalatoborate, tetrachloroaluminate, carbonate, carbonate, carbonate, alkoxide, alkylate, mono-phosphate, carbonate, carbonate, alkyl, mono-alkyl Ser
• methyl sulfate is preferably selected from the group consisting of methyl sulfate, halide, monocarboxylate, hydrogen sulfate, hydroxide, alkoxide, alkyl carbonate, hydrogen carbonate, carbonate, more preferably selected from the group consisting of methyl sulfate, chloride, bromide, iodide, formate, acetate, is more preferably selected from the group consisting of chloride, bromide, formate, methyl sulfate, acetate, hydrogen sulfate, is more preferably selected from the group consisting of formate, acetate, bromide, chloride, hydrogen sulfate, is more preferably selected from the group consisting of formate, acetate, bromide, chloride, is even more preferably selected from the group consisting of formate, acetate.
• acetic acid is used as acid S in step (a) of the process according to the invention.
• “monocarboxylate” means the anion corresponding to a monocarboxylic acid, and is preferably selected from the group consisting of formate and acetate.
• the molar ratio between the total amount of the quaternary ammonium salts of the formula K N A used in step (a) of the process according to the invention to the amount of all compounds of the structure (II) used in step (a) of the process according to the invention is in the range from 0.0001: 1 to 1: 1, preferably 0.001: 1 to 0.1: 1, most preferably 0.025: 1.
• Halide is selected from fluoride, bromide, chloride, iodide, more preferably selected from chloride, bromide, most preferably chloride.
• R ' is methyl if acetic acid was used as the acid S in step (a) of the process according to the invention.
• R ' is hydrogen if formic acid was used as acid S in step (a) of the process according to the invention.
• step (a) is carried out according to methods known to the person skilled in the art.
• the reaction of the alkene of the formula (II) to the monoformates (III-A) and (III-B) or the diformate (III-C) proceeds via the epoxide, as in FIG DE 199 29 196 A1 described.
• step (a) The apparatus for the reaction in step (a) is known to the person skilled in the art. This can be carried out in a standard apparatus (reaction flask with reflux condenser or, for large-scale applications, reactors).
• the reaction after step (a) is preferably carried out at a temperature of 50 ° C. to 100 ° C., more preferably 60 ° C. to 70 ° C. and a pressure of 0.5 to 1.5 bar, preferably 1 bar.
• Step (a) takes place in particular in an aqueous solution.
• organic solvents such as, in particular, toluene, xylene, cumene or benzene are also added in step (a).
• the reaction time depends on the rate of conversion and is preferably between 4 to 10 hours, more preferably 5 to 6 hours.
• the reaction is preferably carried out until at least 50 mol%, more preferably at least 70 mol%, even more preferably at least 80 mol%, even more preferably at least 90 mol%, even more preferably at least 90 mol. -%, most preferably at least 99 mol%, of the compound of structure (II ) used in step (a) has converted to the compounds (III-A), (III-B) or (III-C) mentioned below.
• the crude product RP 1 also comprises water and, if appropriate, organic solvent.
• it may also include formic acid and / or acetic acid. It is advantageous to at least partially remove these constituents from the crude product RP 1 before step (b) is carried out. This is done in particular by distillation.
• an organic solvent can be added before or continuously during the distillation in order to remove excess water, formic acid, acetic acid.
• step (a) preferably at least 50 mol%, more preferably at least 70 mol%, even more preferably at least 80 mol%, even more preferably at least 90 mol%, even more preferably at least 90 mol% , most preferably at least 99 mol% of the water comprising RP 1 immediately after step (a) is complete.
• step (a) preferably at least 50 mol%, more preferably at least 70 mol%, even more preferably at least 80 mol%, even more preferably at least 90 mol%, even more preferably at least 90 mol% , most preferably at least 99 mol% of the formic acid comprising RP 1 immediately after the completion of step (a) is removed.
• step (a) preferably at least 50 mol%, more preferably at least 70 mol%, even more preferably at least 80 mol%, even more preferably at least 90 mol%, even more preferably at least 90 mol% , most preferably at least 99 mol% of the acetic acid comprising RP 1 immediately after the completion of step (a) is removed.
• step (b) of the preferred process according to the invention the at least one compound selected from the group consisting of monoesters (III-A) and (III-B), diesters (III-C) in the crude product RP 1 is saponified.
• “saponification” means the basic cleavage of the compounds (III-A), (III-B) and (III-C) to give the 1,2-alkanediol of the formula (I). According to the invention, “saponification” also includes the term “decarbonylation”.
• Step (b) takes place according to methods known to the person skilled in the art.
• a saponification reagent preferably alkali carbonate, alkali hydroxide, alkali alcoholate, preferably alkali alcoholate, is added and this is allowed to react with the crude product at 10 ° C to 100 ° C, preferably 20 ° C to 70 ° C.
• the preferred alkali metal alcoholate is alkali metal methoxide, more preferably sodium methoxide, even more preferably a methanolic solution of sodium methoxide.
• the preferred alkali hydroxide is sodium hydroxide, in particular an aqueous solution of sodium hydroxide.
• the preferred alkali metal carbonate is sodium carbonate, in particular an aqueous solution of sodium carbonate.
• the saponification reagent is added until a pH of 7.1 to 14, preferably 8 to 12, more preferably 10 to 11, is established.
• the saponification reaction is usually over after 5 minutes to 10 hours, more preferably 0.5 to 2 hours.
• the compounds (III-A), (III-B) are monoformates and the compound (III-C) is the diformate.
• the crude product RP 1 is comprised of at least one compound selected from the monoformates (III-A), (III-B) and the diformate (III-C) with a basic catalyst Kat B selected from alkali or alkaline earth alcoholates of alcohols with 1 to 10, preferably 1 to 4 carbon atoms are added.
• a basic catalyst Kat B selected from alkali or alkaline earth alcoholates of alcohols with 1 to 10, preferably 1 to 4 carbon atoms are added.
• Methylates, ethylates, tert- butylates of sodium, potassium and optionally calcium are very preferred.
• Methylates of sodium and potassium are particularly preferred, and sodium methoxide is particularly preferred.
• the amount of cat B used in step (b) based on the amount of the compound of the formula (II) used in step (a) is then in particular 0.1 to 15 mol%, preferably 0.5 to 13.5 mol%, more preferably 1 up to 10 mol%.
• the decarbonylation with Kat B is typically carried out by adding Kat B to the crude product RP 1 and in particular heating to a temperature of 80.degree. C. to 200.degree. C., preferably 100.degree. C. to 170.degree.
• the decarbonylation is preferably carried out until no more CO is formed.
• step (b) a second crude product RP 2 comprising the ammonium salt K N A and the 1,2-alkanediol (I) is obtained.
• step (c) of the preferred process according to the invention the 1,2-alkanediol (I) is at least partially separated off from RP 2 by distillation.
• the separation by distillation can be carried out by methods known to the person skilled in the art.
• the set temperature and the set pressure at which the distillation takes place depends on the particular structure of the 1,2-alkanediol (I) to be separated off and can be set by a person skilled in the art.
• the mixture M comprising the 1,2-alkanediol (I) is then obtained.
• the mixture M also includes the organic impurities V that form during step (a) and / or step (b) and / or (c) and at least partially with the 1,2-alkanediol (I) in step (c) separated from RP 2 .
• step (a) is carried out in the presence of a quaternary ammonium salt of the formula K N A , the organic impurities V in particular also include aminic organic impurities V.
• the addition Z includes at least one oxide or halide of iron or aluminum.
• Chlorides are particularly preferred as halides. Iron can be in the oxidation state (II) or (III), Fe (III) is preferred.
• the additive Z accordingly preferably comprises at least one oxide or chloride of iron or aluminum.
• the addition Z is particularly preferably selected from FeCl 3 , AlCl 3 , Al 2 O 3 , particularly preferably Al 2 O 3 .
• Al 2 O 3 can be added in any modification, in particular selected from ⁇ -Al 2 O 3 , ⁇ -Al 2 O 3 , ⁇ -Al 2 O 3 .
• a pure 1,2-alkanediol is then obtained, that is, the mass fraction of 1,2-alkanediol according to formula (I) in the end product is at least 80% by weight, preferably at least 90% by weight .
• the crude product is based on Lewandowski and DE 32 29 084 A1 manufactured.
• 1,2-pentanediol is then distilled off from each batch.
• the distillate is divided and 5 g of the following additives ( E7 : 15 g) are added to each 500 g of the distillate: attempt additive V1 without V2 without V3 Zinc chloride V4 Calcium chloride V5 Titanium dioxide V6 zinc oxide E1 Alumina E2 Alumina E3 Alumina E4 Aluminum chloride E5 Aluminum chloride E6 Ferric chloride E7 Alumina E8 Alumina
• the olfactory assessment was carried out as follows: 45.0 g of deionized water were placed in a wide-necked Erlenmeyer flask, heated to a water temperature of 60 ° C. in the drying cabinet (forced-air drying cabinet 63 ° C.) and 5.0 g of the respective sample were added. The odor was then assessed.

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